Computing machine



March 3, 1936. T. o. MEHAN 2,033,045

COMPUTING MACHINE Filed Sept. 8, 1933 4 Sheets-Sheet l INVENTOR' THOMAS 0. MEHAN ATTORNEY March 3, 1936. I Q MEHAN 2,033,045

COMPUTING MACHINE Filed Sept. 8, 1933 4 Sheets-Sheet 2 INVENTOR THOMAS OMEHAN BY%M ATTORNEY March 3, 1936. 'r. o. MEHAN COMPUTING MACHINE Filed Sept. 8, 1955 4 Sheets-Sheet 5 INVENTOR THOMAS OMEHAN ATTO R N EY March 3, 1936. Q MEHAN 2,033,045

COMPUTING MACHINE Filed Sept. 8, 1933 4 Sheets-Sheet 4 WITNESSES )NVENTOR gag/W? THOMAS OMEHAN ATTORNEY Patented Mar. 3, 1936 PATENT OFFICE aosaus comru'rmc momma Thomas 0. Mehan, Nor-wood, Ohio, assigns!- to Remington Rand Ina, Bnlhlo, N. Y., a corporation of Delaware Application September 8, 1933, Serial No. 688,629

12 Claims.

My invention relates to computing machines and more particularly to an interlock between the total key and pin carriage.

The main object of my invention, generally stated, is to provide mechanism to prevent an improper operation of the machine by the operator riding the total key which, ordinarily, under certain conditions results in giving a wrong total and in leaving an amount in the dials after a total has been taken, as will be hereinafter more fully explained.

Regarded from another point of view the main object of the invention is to render it impossible by an improper manipulation of the total key in connection with any one of the digit keys, after a blank stroke has been taken, to set up an additional amount in the machine corresponding to said actuated digit key.

A further and more specific object of my invention is to provide mechanism whereby under certain conditions of use the total key returns the stop carriage to its initial position and under certain other conditions of use, the pin carriage prevents a depression of the total key.

Astill further object of my invention is to provide an interlock of the character referred to which is simple in construction, eflicient in use, and economical to manufacture.

To the above and other ends which will hereinafter appear, my invention consists in the features of construction, arrangements of parts and combinations of devices set forth in the follow ing description and particularly pointed out in the appended claims.

In the accompanying drawings, wherein like reference chraracters represent corresponding parts in the various views Fig. 1 is a fragmentary, isometric view of the front portion of a computing machine with the outer casing and bed plate removed, the view responding to the line 22 of Fig. 7 and looking in the direction of the arrows at said line, and with the left-hand side plate of the frame and other parts omitted.

Fig. 3 is a fragmentary, front elevation with parts in section of the total key, escapement mechanism, one of the numeral keys and some of the associated parts; the keys being shown in normal position.

Fig. 4 is a view similar to Fig. 3, but showing the numeral key depressed, and the relative posia tions of the parts moved thereby.

Fig. 5 is a front elevation similar to Fig. 4, but showing the positions oi. the parts after an actuation of the numeral key and a subsequent depression of the total key with the pin carriage shifted back to initial position and held therein by the depressed total key.

Fig. 6 is a front elevation similar to Fig. 5, but showing the pin carriage moved one step to the left from its initial position and the total key locked thereby against depression.

Fig. 7 is an enlarged, fragmentary, plan view partly in section, the section being taken on the line |--I of Fig. 3 and looking in the direction of the arrows at said line.

Fig. 8 illustrates a printed record showing an example of an improper total and showing an indication that an amount is left in the dials 1 such as would occur in the misoperation of the machine in the event that it was not equipped with the devices of the present invention.

Fig. 9 is a detail, fragmentary, perspective view of a portion of the machine.

In the present instance I have shown my invention embodied in a Remington listing-addingcalculating machine, which is a ten key computing machine of the character disclosed in my United States Patents Nos. 1,835,170, 1,876,719 and 1,899,444. While the present invention may be readily embodied in said machine withbut slight changes in the existing structural features thereof, it should be understood that the invention may be embodied in other formsof computing machines, wherever found available.

In the accompanying drawings I have shown only so much of said machine as may be necessary to arrive at an understanding of my present invention in its embodiment therein.

From a consideration of Fig. 1 it will be seen thatthe frame of the machine by which the various working parts are supported comprises side plates II and II unitedby cross bars I! and I3, by a top plate It and by a base or bed plate I5, the latter being shown in Fig. 2.

The computing and printing operations determined by the set-up from the digit keys, are controlled in the present instance by the usual handle-carrying crank arm l6 secured to the main driving shaft l1, though obviously said shaft may be motor driven. I

The usual ten digit keys l8 and total key is are arranged above the top plate; the stem 01' each key passing through a guide slot in said plate. A reduced depending portion 20 of each key stem passes through a guide slot in a second fixed guide plate 2| and is surrounded by a coiled expansion return spring 22. Each return spring bears at its lower end against the plate 21 and at its upper end against the shoulder formed at the intersection of the body of the associated key I stem and the reduced portion thereof. Each digit key stem also has an. ofi-set depending arm 23 that extends through a guide opening in the plate 2|, all of the arms 23 being arranged in a single row fore and aft of the machine.

The pin carriage, which is designated as a whole by the reference numeral 24, is supported and guided on the cross bars l2 and |3 for movement transversely of the machine beneath the guide plate 2|. This carriage carries nine rows of pins 25 with nine pins arranged in each row. ,Each of these pins is mounted in the carriage for a limited vertical movement therein from an upper inefiective position shown in Fig. 1, to a lower eifective position, shown in full lines in Fig.

5.. The parts are so constructed that each pin remains in either position to which it may be shifted until displaced therefrom, aswill herein-' .after appear. When the carriage is in its normal or initial right-hand position, the left-hand fore and aft row of pins 25 is beneath thedepending arms 23 of the digit keys.

As the carriage moves step-by-step from its initial right-hand position, thefore and aft rows of pins 25 are brought successively into register with the row of depending arms 23, each pin 25 of a row being directly beneath the corresponding arm 23, depending onthe 'value of the keywhich.

carries the arm.

When, the crank arm I6 is actuated, each de pressed pin will arrest the corresponding control rack 26 (spring impelled by its associated-spring 21) in'its proper position to determine the amount to be registered and recorded. At the back stroke of the crankarm Hi the carriage is automatically returned to the right beyond its initial position and eventually comes to rest in such position. During such return movement of;

the can'iage' the lowered effective stops or pins 25 are brought successively into contact with a fixed cam plate 28, thus causing the pins to be elevated by a camming action andrestored to ineffective position on the pin carriage.

This return movement of the carriage may also be efiected at any time with the aid of the usual .correction' key 29, as pointed out in myabove 15, the upper end of the'arm being pivoted at 32 to one end of a'link'33. The opposite end of this link is pivoted at 34 to' an arm 35 which carries a correction key 29 and is connected to the pin carriage to move therewith. A feed rack 38 (Fig. 1) is fixed to the pin carriage to travel therewith. The forwardly projecting teeth 31 on this rack coact with feed dogs 38 and 39 respectively carried by a-dog, rocker or arm 40. Said. dog rocker is pivoted at 4| on a depending car 32 on the fixed guide plate 2|,

4 -as best shown in Figs. 1 and 3. The normally engaged feed dog '38 .is in the nature or a loose Said arm is pivotedat its or stepping dog pivoted at 43 to a depending against the under edge of the fixed dog 39 that a is formed as a laterally projecting lug on the dog rocker. interdental space 31 between the teeth of the feed rack and thus holds'the pin carriage against movement to the left by the power applied thereto by the spring 38. When the dog rocker 40 is lowered by a downward movement around its pivot 4|, the dog 38 is withdrawn from the interdental space and when freed from the engaged tooth of the feed rack will permit a slight forward advance or drop of the carriage until'the same tooth of the rack engages the fixed dog 39, which by this time has moved into the path ofthe racktooth from which the loose dog has just The dog 38 normally extends into anbeen released. This slight drop of the carriage,

which occurs on the down movement of the dog rockerand of a digit key, is less than or a fraction of a full step of the carriage, and is sufiicient to bring the upper end of the dog 38 beneath the adjacent tooth 31 of the feed rack. When the depressed digit key is released, the dog rocker 40 is moved upward by its returning spring. .Said spring-is anchored at one end on a bracket arm 41 of the guide plate 2| and has its lower end connected to an ear 40 on the dog rocker, as shown in Fig. 1. The efiective force of the spring 48 is greater than thatof the spring 45 and causes the upper end of the dog 38 to slide to the right along the under side of the engaged tooth 31 and enter the next interdental space 31 to the right of such tooth as the holding dog 39 is withdrawn from the engaged rack tooth. This enables the carriage to advance the remainder of its distance to complete the step of the carriage, thereby bringing the first fore and aft or denominational rowof pins 25 more fully beneath the row of key actuated arms or plungers 23 and into more complete register with the first of the racks 28. In this movement of the carriage the pressure of the carriage spring 38 overcomes the slight pressure of the spring 45 on the loose dog 38, and the movement of the latter continues until it is ar-. rested by engaging the fixed dog 39, thus holding the carriage against further forward movement.

It will be understood, however; that the carriage is free to be moved to the right either by the correction key 29 or by the automatic action of the arm 3| on the back stroke of the handle actuated crank arm It. At this time the loose dog 38 will be cammed against the force'of its spring 45 out of the interdental space in the rack in which said dog is received and will enter the first registering interdental space when the carriage is arrested and as the carriage starts to move to the left. This is true whether the carriage is returned the distance of one or more teeth of the feed rack.

In order to actuate'the dog rocker at each actuation of a digit key, there'is provided a uni-' versal bar 48 which underliesoiT-set aligned pro- .jections 49 on all of the key stems of the digit keys, to be actuated thereby. Saiduniversal bar is connected at its ends to crank arms 50 and 5| fixed on a rock shaft 52. A link53 is pivoted at its upper end to the crank arm 5|, as indicated at 54, whereas the lower end of said link is pivoted at 55 to the dog rocker 40. It will be understood, therefore, that a depression of 'any digit key will actuate the universal bar and the dog,

rocker controlled thereby and thus advance the carriage one step at each complete actuation of -any digit key.

The total-taking mechanism comprises the total-taking key I9 mounted for vertical movement in guide slots in the plates l4 and 2I and said key is returned to normal position by the associated spring 22, as hereinbefore pointed out. Projecting to the left from the stem of the total key is an arm 56 slotted horizontally at 51. The crank arm of the universal bar is extended beyond its rock shaft to provide an arm 58 formed at the free end thereof with a rearwardly extending lug or projection 59 that extends beneath the arm 56 of the total key. It will be understood, therefore, that when any digit key is held fully depressed, as shown in Fig. 4, a corresponding depression of the universal bar 48 will elevate the projection 59 and prevent a depression of the total key I9. Moreover, when the total key is held depressed, this will elevate the universal bar 48 and prevent a depression of any of the digit keys. Notwithstanding this interlock between the total key and the digit keys, there is at times presented a condition when in the absence of the featuresof the present invention an erroneous total may be entered in the machine and a number left in the totalizer when it is supposed to be cleared, as will hereinafter more clearly appear.

The open end slot 51 in the arm.56 of the total key receives an arm 69 of a bell crank lever SI of a total lock mechanism (Fig. 9). A second arm 62 of this bell crank lever is connected to one end of a link 63 which operates to shift the usual accumulator. engaging and disengaging mechanism (not shown) so that the latter will operate to take a total and clear the accumulator as fully disclosed in my above mentioned patents. Formed integral with thebell crank 60, 62 through a cross bar 64 is a third arm 65 that has its lower end pivoted, at 66, to a rearwardly extending link 61. A pivot rod 68 supports the member 66, 62, 64, 65. The rear end portion of the link 61 is slotted at 69 to receive a headed stud carried by the side plate III and by which the rear end of the link is supported and guided. J

The link 61 has an outwardly projecting pin 1I near its rear end and also has an inwardly and upwardfy projecting lug 12 that terminates in a pointed end, as shown in Figs. 1 and 9. A hook-like latch 13 is pivoted on a headed pin .14 secured to the side plate I8 and is normally held in its elevated position by a spring 19. This latch has a bent over lug which is adapted to be engaged by an engaging nose formed on a separate one way pawl 16 also pivoted on the pin 14. This pawl is normally held in the position shown in Fig. .1 by a spring 11 and is adapted to be engaged by a pin 18 on a keeper plate 19. In the downward movement of the pin 18 from .the Fig. 1 position, the pawl 16 will be moved down around its pivot by said pin independently of the latch 13, the pin passing the pawl at the last part of its movement. On the next upward movement of the pin 18, however,it will turn the pawl in an anti-clockwise direction as the parts appear in Fig. 1. The pawl at this time will engage the lug 15 and actuate the latch to a release it from the pin 1I if the latter is engaged thereby, thus freeing the link 61.

The keeper plate 19 is secured to a shaft and has an outwardly projecting flange M which when the link 61 is in its rearward position engages in front of the lug 12 and prevents said link from moving forward until just prior to the completion of the operating cycle as fully explained in my above mentioned patents.

Blank stroke lock The blank stroke lock has been described in detail in the before mentioned patents, but I deem it necessary to describe it here in order to bring out more forcibly the need of my present supplemental lock or interlock between the total key and pin carriage during the accidental riding on or improper use of the total key.

The blank stroke mechanism comprises the shaft 82 rotatively mounted in bearings in the side plate II and in an upwardly struck bracket arm 83 of the lower guide plate 2|. has a locking hook 64 secured thereto near its left-hand end, as shown in Fig. l. The bill of this hook is adapted to lie beneath the projection 56 of the total key I9 when the stop carriage is displaced from its normal or initial position at the right. This results in looking the total key until the blank stroke of the handle or crank arm I6 is taken. A depending arm 85 is secured to the shaft 82 near the right-hand end thereof and is pivotally connected, at 86, to the forward end of a link 81. The rear end of said link is supported and guided by a pin 88 which projects from the side plate I I and extends through a slot 89 in the link. A latch 90 is pivoted at 9I to the link 81 and has a spring 92 connected thereto so as to normally rock the latch clockwise on its pivot, as the parts appear in Fig. l, the movement of the latch under the pull of the spring being limited by the top plate I4. The latch 90 has a depending toe portion 93 adapted to engage the front face of a vertically disposed lug 94 which is secured to the carriage 24. After every blank stroke of the handle and total taking operation the toe 93 of the latch 96 is held in engagement with the front of the lug 94 by the spring 92 and this in turn holds the engaging end or bill of the hook 84 clear of the projection 56 of the total key I9. It will be seen, therefore, that when the carriage is in its This shaft normal position with the lug 94 thereon engaged by the latch 90, this will resist the rearward movement of the link 81 under the action of the spring 92 thereon and will hold the locking hook 84 out of locking position. However, when the carriage advances one step from normal position, the lug 94 will be released from the latch 90 and the latch and lug will no longer restrain the link 81 against rearward movement under the action of the spring 92 and the locking hook 64 will move to locking position.

The construction thus far described constitutes part of the usual Remington computing machine hereinbefore referred to and is disclosed in my said patents.

Interlock between total key and pin carriage Referring now to the novel interlock of the present invention between the total key and the pin carriage, attention is directed to Figs. 3 to 6 where it will be seen that the stem of the total key I9 is provided with an off-set downwardly projecting arm or finger 95, the lower extremity of which is tapered slightly at 96 to form a cam on the right-hand edge thereof. This is to insure a shifting of the pin carriage to the right, as will be hereinafter more fully described. The escapement rack 36 is provided with an extended shelf-like portion 91 which is out of the path of the finger 95 of the total key- I9 when the stop carriage is in normal position shown in Figs. 1 and 3.

Under normal operation, the machine is actuated in the usual manner by depressing the seout. As soon as this step of the carriage is efiected the latch 90 is no longer restrained by the lug 94 and the spring 92 moves the link 81 rearward until it is arrested by the engagement of the pin 99 with the forward end of the slot 89. This rearward movement of the link 81 rocks the shaft 82 counter-clockwise (as viewed from the righthand side in Fig. 1) causing the bill of the hook 84 to pass beneath the projection 56 on the stem of the total key l9. The total key will thus remain' locked against depression by the hook 84 during two complete operations of the crank arm or handle' During the first operation the hook is temporarily released since the link 81 is moved forward by'a pin 98 on a cam 99 engaging a cam edge loll-of an 'arm llll that is attached to and projects laterally and rearwardly from the link 81. When, however, this takes place, the lug 12 will lie in front of the flange 8| on keeper plate I9 and thus prevent a depression of the total key. Since the carriage is automatically returned to its normal right-handposition, or beyond it, just prior to the completion of the return stroke of the handle or. crank arm Hi, the toe 93 of the latch 90 will have passed to the rear of the position normally taken by the lug 94 before the carriage is in normal position. Therefore, upon the completion of the first operation of the handle the link 81 will be in its rearward position and the total keylocked. It follows that an additional operation or blank stroke of the handle is necessary to condition the machine for total-taking.

During this blank stroke thecarriage 24 will, of course, remain in normal right-hand position and when the link 81 is moved forward by the pin 98 the toe93 will engage the front of the lug 94 thereby holding-the link 8"! in its forward. position. With'the link in this position the bill of the hook 84 is removed from beneath the,projection 56 on the stem of the total key and the total may therefore be taken on the third operation of the handle. 7 L i It is at this point during the operation of the machine that carelessness on the part of the operator would, in the absence of the features of the present invention, permit a wrong totalto be taken, as will now be explained. With the-machine in the condition for total-taking it will be observed that the total key is not locked by hook l4 and cannot be locked by the lug 12 until the operating handle is started 0111128 forward stroke. Therefore, with the machine thus conditioned for total-taking, let us assume that the operator ac- 1 cidentally depresses a digit key and as it is allowed to return to elevated position, depresses a total key (as illustrated in Fig. 5) then the following conditions would result in the absence of the features of the present invention. The hook 84 would not have had chance to move beneath the projection 56 of the total key and the depression of the digit key would result in setting up an additional stop 25 and immediately taking a total which would include the amount of the accidentally depressed digit key. As aniexample of this attention is directed to Fig. 8 which shows three amounts A, B and 0 set up in the machine,

the blank stroke being indicated bythe space D.

In this instance the 1 key, we will assume, was depressed and as it was allowed to restore, the

total key was depressed permitting a total-taking proper manipulation of the total key in connec-- ,tion withany one of the digit keys (after a blank stroke has been taken) to setup an additional amount in the machine and immediately 'follow with a total-taking operation.

In the'event that the blank stroke of a handle has been taken and the operator should then depress a'digit key while dwelling or riding on the depressed total key the following operation of the parts will result. The stop pin 25 corresponding to the depressed digit key will be moved down to efiective position las indicated in Fig. 4, and-a slight forward advance or drop of the carriage from the Fig. 3 to the Fig. 4 position will be brought about. This will advance the left-hand edge of the table-like portion 91 of the carriage into the path of the cam edge 96 on the totaliz er key', and as the latter moves from the Fig. 4 to the Fig.5 position will return the carriage to the right and hold it in its normal position. The result of this is to bring the lowered pin to the right of the-first rack 26 so as to be ineifective thereon, thus preventing the amount determined by said pin from being set up. The depression of the total key at this time results in it being automatically locked by the latch 13 which in turn locks the digit keys. It is therefore necessary to actuate the handle or crank l6 which results in overthrowing the carriage to the right and wiping out or restoring the depressed pin 25 by the cam 28.

If, however, a full depression ofthe total key takes place in advance of the depression of any digit key, then the arm 95'will be brought into the path of movement of the carriage and the latter cannot be advanced from its normal position and, of course, all of the digit keys will remain lockedat this time.

If, on the other hand, a digit key is depressed first 'in the circumstances indicated above and is allowed to return-to normal position, thus affording an advance of the carriage for a full step, then this will bring the table-like portion 91 of the carriage beneath and in the path of the arm on the total key and will pression of said key.

From the foregoing description it will be readily apparent that after a blank stroke is taken it is impossible to set up an additional amount in the machine and immediately follow with a total-taking operation by depressing a digit key and a riding of the total key, due to the arm prevent a"de 95 and'the part 91 on the carriage. In other words, if a digit key has been depressed'allowing the carriage to move slightly tothe left and the operator then depresses the total key before allowing the digit key to restore, the cam surface.

on the total key then restores the carriage to normal position thus preventing any stops from coming in line with the adding rack 26. If, however, the operator allows the digit key to restore before trying to depress the total key, the

reference to the total key l9 also applies to the control of and by the sub-total key, and in said Remington machine an actuation of the sub-total key I02 results in actuating the total key l9.

From the foregoing description it will be understood that I am enabled to attain the advantages pointed out by very simple additions to the above mentioned Remington computing machine without modifying theexisting structural features thereof. However, as hereinbefore pointed out the invention is not restricted to embodiment in v such machines and various changes may be made in the construction without departing from my invention as it is defined in the accompanying claims.

What I claim asnew and desire to secure by Letters Patent is:

1. In a computing machine, the combination of a pin carriage, a total key, and interlocking means between said total key and carriage so constructed and arranged that a full step advance of the carriage from its initial position will interpose a fixed part on the carriagedirectly in the path of a part fixed directly to the total key and prevent an actuation of said total key.

2. In a computing machine, the combination of a pin carriage, a total key, and interlocking means between said total key and carriage so constructed and arranged that an actuation of said total key after the carriage has advanced a part onlyof a complete step from its initial position will result in shifting said carriage back to and in holding it in its initial position.

3. In a computing machne, the combination of a pin carriage, a total key, and interlocking means between said total vkey and carriage so constructed and arranged that a fullstep advance of the carriage from its initial position will interpose said carriage in the path of and prevent an actuation of said total key, said interlocking means comprising a locking member fixed on the carriage. and cooperating directly with a locking member fixed directly to said total key.

4. In a computing machine, the combination of a pin carriage, a total key, and interlocking means between said total key and carriage so constructed and arranged that an actuation of said total key after the carriage has advanced a part only of a complete step from its initial position will result in shifting said carriage back to and in holding it in its initial position; said interlocking means having one element thereof carried directly by said carriage and the other element thereof carried directly by said total key.

5. In a computing machine, the-combination of a pin carriage, digit keys for setting pins on said pin carriage, a total key, and interlocking means between said total key and carriage so constructed and arrangedthat when the machine is otherwise conditioned to permit an actuation of the total key a full step advance of the carriage from its initial position will result in bringing the carriage into the path of the total key and in locking said key against actuation.

6. In a computing machine, the combination of a pin carriage, digit keys for setting pins on said pin carriage, control racks with which the pins on said carriage coact, a total key, and interlocking means between said total key and carriage so constructed and arranged that an actuation of said total key aftera pin has been set and the carriage has been advanced a part only of a complete step from its initial position by the depression of a digit key will result in shifting said carriage back to and holding it in its initial position, thereby shifting and maintaining the actuated pin out of cooperative relationwith any of said control racks during a total taking operation.

7. In a computing machine, the combination of a pin carriage, a total key, and a locking member carried by said total key, the pin carriage and apin carriage, digit keys, a total key, and a looking member carried by said total key and provided with a cam, said carriage cooperating with the locking member so that an advance of the carriage one complete step from its initial position will bring it into the path of said locking member and prevent an actuation of the total key whereas the advance of the carriage for a part only of a complete step from its initial position by a mere depression of a digit key will bring the carriage into cooperative relation with said cam so that a depression of the total key at this time 7 will result in camming the carriage back to initial position and in holding it in such position as long as the total key is maintained depressed.

9. In a computing machine, a pin carriage, a manually operated total key, and locking mechanism controlling said carriage and key and being constructed and arranged so that under certain operating conditions of the machine the said looking mechanism serves to lock the total key against depression dependent on the position of said carriage, and including means which under certain and an extended horizontal shelf -likeportion supportedby and movable with. said carriage, said parts being so constructed and arranged that when said carriage is in itsnormal position the shelf portion supported thereby is clear of said finger, and upon depression of said total key after an advance of the carriage for a part only '01 a complete step the said finger coacts with said shelf to restore the carriage to its initial position and block and advance movement thereof thus locking the carriage in normal position, and when said key is in its normal position and the carriage is displaced a full step'from its normal position said shelf will be carried beneath said finger thus locking said key against depression, thereby preventing a misoperation of the machine.

11. In a computing machine in which a blank stroke-of the handle is required before total-taking in order to provide a proper operation, the

combination of a pin carriage, a total ,key and interlocking means between said total key and pin carriage including means for automatically returning the carriage to and holding it in the home position when the total key is depressed and in the event that a partial advance step of the carriage has been eflected, thus preventing an effective setting up of a pin in the pin carriage -in the event the total key has been fully depressed.

12. In a computing machine in-which a blank stroke of the handle is required before total taking bination of a pin carriage, digit keys, 9; total key, and. interlocking means between said total key and pin carriage which prevents an actuation of the total key in the event that the carriage has advanced a complete stepfrom initial position and which restores thecarriage to its initial position in the event that the carriage has advanced a part only of a step from its initial position, whereby an actuation of a digit key before totaltaking and after a blank stroke does' not result 0 

